The present invention relates generally to vibration suppression for turbine blades.
Various types of vibration suppressors are known to be used for the blades of both steam and gas turbines and for compressors and the like. Since the individual blades need to be fastened at one end to a rotor, vibration suppressors are employed in order to eliminate the danger of fractures due to vibrations. Prior techniques for reducing vibration consist of soldering a wire into the blades, inserting damping rods within the individual blades, or riveting or soldering tierods to the blades.
The known turbine blade vibration suppressors have various disadvantages especially when used in gas turbines which have a high output and that operate at high temperatures. For example, a soldered damping wire cannot be used in an engine having high operating temperatures because the solder might melt. Damping rods which are inserted into the blades and have a certain amount of play will eventually result in wear of both the rods and the blade openings so that the damping effect will be lost.
Accordingly, it is an object of the present invention to provide a vibration suppressor for a turbine which is attached to blades of the turbine in a simple manner and which effectively reduces vibrations within the turbine blades.
The present invention accomplishes these and other objects in that the damping elements for the turbine blades include damping tubes which are expanded between the individual adjacent turbine blades. Wires are inserted in the tubes axially with respect to the longitudinal axis of each tube to further stabilize the damping tube, especially in turbines in which the blades are spaced relatively far apart.
The vibration suppressor of the present invention has a particular advantage over the prior art in that expansion of the damping tubes between the turbine blades will prevent a shifting of the damping tube. By maintaining the damping tube in a proper position the turbine blades are in turn retained in their proper position, thus making it possible to reduce vibrations to a minimum.
Another feature of the present invention provides for crimping of the expanded portions of the tube to secure the wire which is inserted through the tube. Additionally, an end portion of the damping tube which extends through the last blade of each circumferential segment is expanded to securely fix the tube with respect to the final blade.
The crimping of the wires at the expanded portions of the damping tubes prevents the wire, which is inserted into the damping tubes, from moving within the tube. Since the damping tubes are employed across the perimeter of a row of blades or buckets, the damping tube must be widened at the final blade, preferably by a center punch, so as to secure the tube to the last blade.